What alterations would have to be made for a solution of a weak acid to have a lower pH than a solution of a strong acid?

1 Answer
anor277
Jun 13, 2018

Add some conc. #HCl(aq)#...?

Explanation:

You gots a weak acid, for which #H_3O^+# depends on the equilibrium...

#HX(aq) +H_2O(l) rightleftharpoonsH_3O^+ + X^-#

And #K_a=([H_3O^+][X^-])/([HX(aq)])#

And as always...#pH=-log_10[H_3O^+]#...and so to REDUCE the #pH# we would have to add a STRONG ACID … conc, #HCl#, approx. #10*mol*L^-1# is a good bet...this dissociates completely to give stoichiometric #H_3O^+#...and thus when it is added to solution (and we follow PRECISELY this order of addition of acid to water!), #pH# should DECREASE markedly without grossly increasing solution volume...

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